EC Number   |
Substrates |
Organism |
Products |
Reversibility |
|---|
   2.7.7.79 | more |
in vivo Thg1 catalyzes 3'5' polymerization on tRNAHisC73, but not on tRNAHisA73 |
Saccharomyces cerevisiae |
? |
- |
? |
| 2.7.7.79 | more |
the enzyme also catalyzes 3'-5' extension of a polynucleotude chain by multiple nucleotides. Unlike the addition of G(-1), the reverse polymerisation activity is template-dependent, recognizing G*C WatsonCrick base pairs. Moreover, reverse polymerization is not specific for tRNAHis or for starting at the (-1) position of tRNA, provided that the activated (triphosphorylated) form of the tRNA substrate is used in the assays |
Saccharomyces cerevisiae |
? |
- |
? |
| 2.7.7.79 | more |
retention of the 5'-triphosphate is correlated with efficient 3'-5' reverse polymerization. The intrinsic rate of removal of diphosphate from the G-1 residue of base-paired tRNAHis substrates is slow. Rates of diphosphate removal depend on the identity of the NTP included in reactions. The GTP 3'-OH is required to stimulate diphosphate removal |
Saccharomyces cerevisiae |
? |
- |
? |
| 2.7.7.79 | more |
when full-length tRNAHis (lacking the G-1 residue) is used as a substrate, TLP exhibits a strong preference for use of GTP over ATP for 5'-end activation. Product formation is extremely slow in the presence of only ATP. With a 5'-truncated substrate missing the +1 nucleotide, both ATP and GTP are used with relatively equal efficiency for activation |
Bacillus thuringiensis serovar israelensis |
? |
- |
? |
| 2.7.7.79 | more |
enzyme activity assay with purified recombinant palm domains from Methanosarcina acetivorans Thg1 (MaPalm, amino acids 1-141) incubated with radiolabelled Escherichia coli tRNAHisDELTAG-1 and GTP. Substrate specificity analysis with tRNAHis substrates differing in the discrimination position 73, and different nucleotides, i.e. radiolabelled GTP and unlabeled GTP, ATP, UTP, and CTP, analysis of Thg1 sequence determinants for extended reverse polymerization. The palm domain of Thg1 is sufficient for catalytic activity |
Methanosarcina acetivorans |
? |
- |
- |
| 2.7.7.79 | more |
enzyme activity assay with purified recombinant palm domains from Pyrobaculum aerophilum Thg1 (PaPalm, amino acids 1-150) incubated with radiolabelled Escherichia coli tRNAHisDELTAG-1 and GTP. PaThg1 repairs truncated tRNA substrates. Substrate specificity analysis with tRNAHis substrates differing in the discrimination position 73, and different nucleotides, i.e. radiolabelled GTP and unlabeled GTP, ATP, UTP, and CTP, analysis of Thg1 sequence determinants for extended reverse polymerization. PaThg1 adds a single nucleotide to the guide RNAs and also to the control hammerhead ribozyme RNAs in the presence or absence of target RNAs. The palm domain of Thg1 is sufficient for catalytic activity |
Pyrobaculum aerophilum |
? |
- |
- |
| 2.7.7.79 | more |
human Thg1 (hThg1) catalyzes the G-1 addition reaction for both human ctRNAHis and mtRNAHis through recognition of the anticodon. While hThg1 catalyzes consecutive GTP additions to mtRNAHis in vitr (consecutive G-2 and G-3 addition to pppG-1-hmtRNAHis), it does not exhibit any activity toward mature pG-1-mtRNAHis. hThg1 can add a GMP directly to the 5'-terminus of mtRNAHis in a template-dependent manner, but not to ctRNAHis. Acceleration of the diphosphate removal activity before or after the G-1 addition reaction is a key feature of hThg1 for maintaining a normal 5'-terminus of mtRNAHis in human mitochondria. The GUG to GAA conversion completely abolishes the ability of hThg1 to catalyze the adenylylation of both tRNAs, anticodon variants of hmtRNAHisGAA and hctRNAHis GAA, respetively, suggesting that hThg1 recognizes both of them in a His anticodon-dependent manner. The mobility of mtRNAHis is significantly faster than that of hctRNAHis on a native-PAGE gel, further suggesting a structural difference between them that is consistent with secondary structure predictions |
Homo sapiens |
? |
- |
- |
| 2.7.7.79 | more |
IhTLP is catalytically active in vitro, and catalyzes a significant tRNA repair reaction in vitro, adding up to 13 nucleotides to restore a truncated tRNAHis |
Ignicoccus hospitalis |
? |
- |
- |
| 2.7.7.79 | more |
kinetic analysis and substrate specificity, overview. GTP can be directly conjugated with 5'-triphosphorylated tRNAHis without ATP activation. UTP is a poor substrate. The reaction efficiency of GTP addition is affected by the structure of the opposite base at position 73. No activity with ATP, 8-oxo-GTP, isoGTP, and 8-bromo-GTP instead of GTP. The activity with CTP, 2-aminopurine, 7-deaza-GTP, ITP, and UTP depends on the tRNAHIs substrate identity |
Candida albicans |
? |
- |
- |
| 2.7.7.79 | more |
the enzyme is active in an in vitro activity assay with radiolabelled Escherichia coli tRNAHisDG-1 and recombinant wild-type IhThg1 enzyme. IhThg1 displays reduced enzyme activity with yeast tRNAHisDG-1, which encodes an A73 discriminator base in compared to Escherichia coli tRNAHisDG-1 with a C73 discriminator base. Radioactive product formation is observed in the presence or absence of ATP, suggesting that IhThg1 does not require ATP-dependent activation, but can utilize GTP, as observed for other archaeal-type Thg1 enzymes. . Substrate specificity analysis with tRNAHis substrates differing in the discrimination position 73, and different nucleotides, i.e. radiolabelled GTP and unlabeled GTP, ATP, UTP, and CTP, analysis of Thg1 sequence determinants for extended reverse polymerization. IhThg1 is active despite lacking conserved RNA recognition motifs. The palm domain of Thg1 is sufficient for catalytic activity |
Ignicoccus hospitalis |
? |
- |
- |
